U.S. patent application Ser. No. 524,637 filed Aug. 19, 1983, now U.S. Pat. No. 4,559,541, having the same inventor and same assignee as the instant patent application, is relevant but is not "prior art" to the instant application because the two applications are copending applications having the same inventor and nonoverlapping claims.
U.S. Pat. No. 3,355,740 depicts a log periodic antenna having two zig zag structures. However, the antenna shown in this patent differs from the instant invention in that: (1) Its two structures are not substantially coplanar, preventing its usability as a conformal antenna and prohibiting its fabrication by printed circuit techniques; (2) It is fed differently. In FIGS. 3 and 4, the feed method is not shown in detail; however, the feed element does not double back between radiating structures as in the present invention; therefore the FIG. 3, 4 antenna is less compact than the present invention. In FIG. 5, the feed element is contained within one of the radiating structures, which makes for a longer path and therefore greater loss than with feed line 18 of the present invention; (3) The radiating structures in the referenced patent are overlaid with respect to each other, not side-by-side as in the present invention. As a consequence, the present invention's radiated beam is advantageously narrower in the common plane; and (4) the patent shows sharp zig zags rather than the more compact S-shaped loops of the preferred embodiment of the present invention.
USSR Pat. No. 148118 shows a log periodic antenna with trapezoidal tooth structures, not zig zag radiating loops as in the present invention. The trapezoidal tooth structures are not substantially coplanar as are structures 3, 5 of the present invention. The antenna depicted in the referenced patent cannot be fabricated on a single dielectric board using printed circuit techniques as in the present invention.
Japanese patent publication no. 34058/70 shows an antenna having zig zag structures. However, FIG. 2 shows that the structures are resonant because they are connected to the outside of central coaxial feed line 2. On the other hand, structures 3, 5 of the present invention are nonresonant. Feed element 2 in the referenced patent is not fabricated of printed circuit elements as can be feed line 18 of the present invention. The zig zag structures in the reference are overlaid, not side-by-side as are structures 3, 5 of the present invention.
U.S. Pat. No. 4,286,271 shows a log periodic monopole antenna which differs from the antenna of the present invention in that: (1) the zig zag structures are not substantially coplanar; (2) the zig zag structures are not located side-by-side; (3) the feed element is not shown to be constructible using printed circuit techniques (there are difficulties in feeding a noncoplanar array of this type because of the interaction between the feed line and the radiating elements); and (4) in the patent, the two zig zag structures are fed out of phase, not in phase as are structures 3, 5 in the present invention.
Other references are U.S. Pat. Nos. 3,383,693, 3,541,564, 3,633,207, 3,696,438, 3,732,572, 4,152,706, and 4,260,988; and United Kingdom patent specification no. 905,417.